The Use of Ambient Noise for Building and Soil Characterisation

This chapter deals with diverse problems related to measurements of the ambient noise and their application for determination of soil or building properties. Although microtremors are studied since the first half of the 20th century, the number of inves tigations rapidly increased following the article by Nakamura in 1989. In the last two decades a host of methods and procedures emerged, some of which found their way into the everyday practice of seismologists and engineers dealing with the problems of site affects and soil-structure interaction.

Even though the theoretical background of the H/V ratio technique was initially not completely clear (and controversies still exist), its simplicity and low cost appealed to many. In his article in this chapter Y. Nakamura revisits the fundamental assumptions behind the concept of the H/V ratio and presents examples of its use. He clearly advocates the interpretation in terms of body waves, at least around the fundamental frequency of the soil.